Washington (AFP) – US President Donald Trump was set Thursday to target social media giants like Twitter, which he accuses of bias against him, with an executive order opening them to new regulation.”This will be a Big Day for Social Media and FAIRNESS!” Trump said on Twitter.The wording of the executive order remained under wraps. A White House spokeswoman on Wednesday said only that it would be “pertaining to social media.”But Trump is on the warpath against Twitter after the platform for the first time labelled two of his tweets, on the increasingly contentious topic of mail-in voting, with…